Propagation News

| January 27, 2013

And now the solar factual data for the period from Friday the 18th to Thursday the 24th of January, compiled by Martin Harrison, G3USF, on Friday the 25th of January.

Two large and magnetically complex groups rotated off the visible Sun, leading to markedly quieter conditions. At the start of the period a C5 flare was reported but subsequent days brought only a few small C-class flares, then none from the 21st to the 24th. Solar flux levels declined from 123 on the 17th to 103 on the 24th. The average was 108 units, compared with 150 the previous week. The 90 day solar flux average on the 24th was 120 – three units down on last week. X-ray flux levels declined from an average of B5.9 units to B2.1. The geomagnetic field was quiet or no more than slightly unsettled every day except the 18th, when the Ap index was up to 9. Ap levels as low as 1 were reported on the 22nd, 23rd and 24th, and the average over the period was less than 5 units. Solar wind data from the ACE spacecraft showed a decline from 487 kilometres per second on the 19th to 285 kilometres per second on the 23rd. Particle densities reached 28 per cubic centimetre on the 18th but were mostly in single figures. Bz ranged between plus and minus five nanoTeslas on the quiet days – apart from the 19th, which varied between minus 21 and plus 17 nanoTeslas. Aided by the low level of geomagnetic activity MUFs reached or slightly exceeded predicted values on most days. Radio aurora was reported on the 18th but only from northern Scotland.

Finally, the forecast for the coming week. The quieter side of the Sun is expected to be looking our way. Solar activity is expected to be low or very low, with only occasional C class solar flares. There is only a small chance of large solar flares. Solar flux levels should decline further, possibly below 100. However, they may start rising by the end of the week. Geomagnetic activity could be up slightly today as a consequence of a filament eruption on the 23rd but, otherwise, quiet levels are likely to prevail. MUFs during daylight hours at equal latitudes should continue to be around 25MHz for the south and 22MHz for the north. Darkness hour lows should be about 8MHz. Paths this week to South America should have a maximum usable frequency with a 50 per cent success rate of around 33MHz. The optimum working frequency with a 90 per cent success rate is about 25MHz. The best time to try this path will be between 1200 and 1700UTC.

And that’s all for this week from the propagation team.

Category: GB2RS Propagation News

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